1. Field of the Invention
The invention relates to a joint for connecting wooden beam members, which are advantageously made of so-called laminated veneer lumber, to each other. The invention additionally relates to the use of the joint in roof truss structures.
2. Description of the Prior Art
In roof truss structures, the joints between the beams are subject to great stresses. There is usually no torque present, but the tensile and compressive stress loads may be over 20 N/mm.sup.2, and thus they may rise up to 20-30 tonnes. It is known to connect the members to each other by means of, for example, nails, bolts or so-called nail plates, the plate having been punched and the "nails" thereby obtained having been turned 90.degree..
Since, by means of a nailed joint, it is possible to transfer great compressive and tensile forces only by using a considerably large number of nails, there is the risk that the dimensions of the joint elements have to be increased in order to make room for the number of nails required. Furthermore, nailing is almost handwork, and therefore expensive.
Furthermore, these solutions are not good esthetically, which is a factor to be taken into account when the joint will remain visible, for example in the truss structures of large sports halls.
In addition to their outer appearance, their disadvantages include poor fire resistance, since the metal bolts or metal nails on the surface of the structure heat up very rapidly and conduct heat to the inside of the beams. By using these structures it is very difficult to achieve the 1-hour fire-resistance rating often required.
Furthermore, if the nails used are too thick, they break the wood fibers and cause notching.
Since metal does not react to humidity in the same way as wood does, variations in humidity will cause deformations in the area of the joint and produce forces which thereby weaken the joint.